1. Field of the Invention
The present invention relates to an article pickup apparatus and an article pickup method for picking up an article randomly piled in a three-dimensional space using a robot including a grip unit.
2. Description of the Related Art
As an apparatus of this type, conventionally, there is known an apparatus configured to recognize a position of an article by applying three-dimensional matching processing to a three-dimensional point set obtained by measuring articles randomly piled using a three-dimensional measurement instrument. This apparatus is described, for example, in Japanese Laid-open Patent Publication No. 2011-179909 (JP2011-179909A). Further, an apparatus configured to measure articles randomly piled using a three-dimensional measurement instrument and then extract a region able to be gripped by a grip unit is also known. This apparatus is described, for example, in Japanese Laid-open Patent Publication No. 2011-093058 (JP2011-093058A).
In the apparatus described in JP2011-179909A, while a three-dimensional model pattern of an article is previously acquired from a CAD model or the like, surfaces of articles in a three-dimensional space are measured using a three-dimensional measurement instrument and a three-dimensional point set (an distance image) is acquired, and then the three-dimensional point set is divided into partial regions surrounded by an edge extracted from the three-dimensional point set. Then, initially, one of the partial regions is set as an article region, and both matching processing of the three-dimensional model pattern for the article region and update processing for adding another partial region to the article region are repeated to measure positions and postures of the articles.
In the apparatus described in JP2011-093058A, a grip region including a grip mechanism region determined by a grip mechanism and a grip portion region determined by a grip portion of a target gripped by the grip mechanism is previously stored, and a region equal in size to the grip region and a region where an article is present in the entire region equal in size to the grip portion region but the article is not present in a region equal in size to the grip mechanism region is extracted as a grippable region.
However, in the apparatus described in JP2011-179909A, it is necessary to previously prepare a three-dimensional model pattern for each type of article, and therefore, time and effort are needed. In particular, regarding a large number of types of articles, it is necessary to prepare model patterns for the number of types and therefore, much time and effort are needed. Further, for an indefinitely shaped article, it is inherently difficult to prepare a model pattern, resulting in difficulty in an application thereof. Further, when a grip unit is moved to a pickup position determined by a position posture of an article, a collision between another article and the grip unit may occur.
Further, in the apparatus described in JP2011-093058A, it is necessary to previously set a grip portion region of an article. In addition, there occurs a case where the grip portion region is not exposed on a three-dimensional measurement instrument side in some positions and postures of the article and in this case, it is difficult to pick up the article.